D.C. weather: Storm Janus brings snow, icy conditions to region

D.C. weather: Storm Janus brings snow, icy conditions to region

A winter storm slamming the Eastern United States this week dropped several inches of snow and sleet across Washington and the Delmarva Peninsula, stranding hundreds of drivers and forcing officials to temporarily close several major roadways.

As of Thursday night, more than 100 vehicles had been found in a tunnel on the southbound I-95 in Salisbury, Md., after being stranded for hours.

The National Weather Service issued winter storm warnings from Virginia to Maine and winter storm watches in Illinois and Pennsylvania.

The massive storm, which has been dubbed a bomb cyclone by the National Weather Service, did not produce the second-largest snowfall total this week behind Monday’s blizzard. Instead, it left 14.2 inches of snow in Yardley, Pa., 14.3 inches in Pittsburgh, 12.2 inches in Baltimore and 11.1 inches in New York City.

Forecasters say the storm system, which crossed the Atlantic from the southern Plains over the Gulf of Mexico, pulled away from the Mid-Atlantic area Thursday morning.

How does the term bomb cyclone work?

Forecasters use the term “bombogenesis” to describe a low-pressure system, a rare phenomenon that causes heavy snow, extreme winds and low visibility to rip through large geographical areas.

A bomb cyclone is defined as a storm system with a significant dip in the pressure of a storm system — a motion also known as “bombogenesis.” When the storm centers south of New England, the pressure drops by at least 24 millibars in 24 hours and creates the expected dramatic drop in pressure.

How did weather forecasters determine whether a specific storm system would likely to produce a bomb cyclone?

Forecasters use three measures to determine whether a given storm is likely to produce a bomb cyclone, said Timothy Hoefer, a scientist at the National Oceanic and Atmospheric Administration’s Jet Propulsion Laboratory in Pasadena, Calif.

The two most important measurement systems are AccuWeather’s so-called Global Forecast System and GRACE, a satellite system from NASA and the European Space Agency that monitors atmospheric pressure over large geographic areas.

Weather service Meteorologist Rick Knabb explained that extreme areas with colder air can be forecast to produce extremely strong storms with lower air pressure and very strong winds that could reach hurricane force.

“In regions of high altitude that are often exposed to snow, we can pinpoint which areas will be at risk,” Knabb said.

Hoefer said the difference between such strong storms and the lowest category of a bomb cyclone — and a storm system that “doesn’t fall out of the sky” — is how far south the centers of the storm are located.

Hoefer said he expects a bomb cyclone and other strong cyclones will become more frequent and more frequent, particularly in the North Atlantic.

How has DC weather changed because of climate change?

Weather experts say there is a growing consensus that there is a connection between climate change and more severe weather events.

Weather service Meteorologist Tom Kines said there is an even greater consensus that the nation’s weather could continue to change into the future.

“We’ve only seen a very small slice of the future storms. There are probably going to be a lot more of them,” Kines said.

The debate over whether storms will increase in severity and frequency in the coming years heated up in 2011, when a government study showed that the nation’s total number of devastating tornadoes has nearly doubled since 1970.

Part of the increase can be attributed to increased atmospheric instability caused by a combination of manmade climate change and warmer air temperatures.

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